During visits over the years to Friends School Haverford, John C. Haas told students how he used to ride to kindergarten there in his family's pony cart.

On Wednesday, the school learned that the philanthropist and retired chairman of Rohm & Haas Co., who died in April at 92, left $500,000 to the tiny elementary school he attended in the 1920s.

Michael Zimmerman, head of the 125-year-old private school, said the money would help fund programs for a planned addition of seventh and eighth grades, and bolster financial aid.

"Happily we're in the position of being able to make wonderful use of what for a small school is a big gift," Zimmerman said.

After six years of enrollment declines, Friends School Haverford, on Buck Lane, has 111 students registered for the fall. Tuition for 2011-12 will range from $9,000 for half-day pre-kindergarten to $20,150 through sixth grade.

A member of the Class of 1930, Haas remained a supporter of the school. Two years ago, he attended a holiday program and toured the campus gardens, greenhouse, and wetlands.

In a 2007 interview in the school's magazine, Links, he told Martha B. Bryans, a former head, that he was "a shy little guy" when he arrived at school as a kindergartner in a pony cart.

His family did not have a car at the time, he said, recalling the ride down Lancaster Avenue from his home in Haverford. The other students, taken with the cart and pony, were given rides around the school's oval driveway.

Haas discovered his aptitude for science as a youngster. After the fourth grade, he transferred to Episcopal Academy, from which he graduated in 1936. After earning his degree from Amherst College in 1940, he served in the Navy in World War II and completed graduate work at Massachusetts Institute of Technology.

He joined Rohm & Haas as a chemical engineer. Before retiring in 1983, he held many positions at the company his father founded in 1909.

Friends School had hoped Haas would be able to take part in its 125th anniversary celebration last year, but his health did not permit it, Zimmerman said.

He said that Haas' generosity would help the school with new programs it will offer when it adds a seventh grade in the fall of 2012 and an eighth grade in 2013. The expansion will allow students who are sixth graders this fall to complete middle school there.

Even with the addition of seventh and eighth grades, the school intends to remain small, according to Zimmerman.

"It's part of who we are as a school," he said. "We are not looking to grow a lot."